/// <summary>
        /// Constructor.
        /// </summary>
        public GameOverScreen()
            : base("Game Over")
        {
            // Create our menu entries.
            MenuEntry resumeGameMenuEntry = new MenuEntry("Retry");
            MenuEntry quitGameMenuEntry = new MenuEntry("Back to main menu");

            // Hook up menu event handlers.
            resumeGameMenuEntry.Selected += OnCancel;
            quitGameMenuEntry.Selected += QuitGameMenuEntrySelected;

            // Add entries to the menu.
            MenuEntries.Add(resumeGameMenuEntry);
            MenuEntries.Add(quitGameMenuEntry);
        }
        /// <summary>
        /// Constructor.
        /// </summary>
        public PauseMenuScreen()
            : base("Paused")
        {
            // Create our menu entries.
            MenuEntry resumeGameMenuEntry = new MenuEntry("Resume Game");
            MenuEntry quitGameMenuEntry = new MenuEntry("Quit Game");

            // Hook up menu event handlers.
            resumeGameMenuEntry.Selected += OnCancel;
            quitGameMenuEntry.Selected += QuitGameMenuEntrySelected;

            // Add entries to the menu.
            MenuEntries.Add(resumeGameMenuEntry);
            MenuEntries.Add(quitGameMenuEntry);
        }
        /// <summary>
        /// Constructor fills in the menu contents.
        /// </summary>
        public MainMenuScreen()
            : base("Main Menu")
        {
            // Create our menu entries.
            MenuEntry playGameMenuEntry = new MenuEntry("Play Game");
            MenuEntry optionsMenuEntry = new MenuEntry("Level Select");
            MenuEntry exitMenuEntry = new MenuEntry("Exit");

            // Hook up menu event handlers.
            playGameMenuEntry.Selected += PlayGameMenuEntrySelected;
            optionsMenuEntry.Selected += OptionsMenuEntrySelected;
            exitMenuEntry.Selected += OnCancel;

            // Add entries to the menu.
            MenuEntries.Add(playGameMenuEntry);
            MenuEntries.Add(optionsMenuEntry);
            MenuEntries.Add(exitMenuEntry);
        }
        /// <summary>
        /// Constructor.
        /// </summary>
        public OptionsMenuScreen()
            : base("Level Select")
        {
            // Create our menu entries.
            levelSelectEntry = new MenuEntry(string.Empty);

            SetMenuEntryText();

            MenuEntry back = new MenuEntry("Back");

            // Hook up menu event handlers.
            levelSelectEntry.Selected += levelSelectEntrySelected;
            back.Selected += OnCancel;

            // Add entries to the menu.
            MenuEntries.Add(levelSelectEntry);
            MenuEntries.Add(back);
        }